Apparatus for advancing and working plastic materials



; wflyfg/ Feb. 7, 1950 HENNlNG 2,496,625 APPARATUS FOR ADVANCING WORKING PLASTIC MATERI Filed NOV. 13, 1946 2 Sheets-Sheet 1 IIIIIIIIIIII 1,

INVENTOR GE. HE N/NG A T TORNEY Feb. 7, 1950 e. E. HENNING APPARATUS FOR ADVANCING AND WORKING PLASTIC MATERIALS 2 Sheets-Sheet 2 Filed Nov. 13, 1946 G W m H i 6 ATTORNEY Patented Feb. 7,

APPARATUS FOR ADVANCING AND WORK- ING PLASTIC MATERIALS George E. lienning naltlmorc, Md., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application November 13, 1946, Serial No. 709,478

This invention relates to apparatus for advancing and working plastic materials, and more particularly to extrusion screws for simultaneously forcing plastic material through extrusion apparatus and plasticizing the material.

In the manufacture of extruded products, such as insulated conductors, plastic material, such as thermoplastic compounds or compounds including rubber or synthetic rubber-like materials, sometimes are milled to thoroughly mix and plasticize the material so that it may be extruded properly. The material then is inserted into an extruder, which extrudes the material upon a conductor, while the material is in a plastic condition. Such working operations are relatively expensive and require considerable handling of the material. In the past, there has been no apparatus for reducing or substantially eliminating the necessity of the working operations prior to the insertion of the material into the extruder.

An object of the invention is to provide new and improved apparatus for advancing and working plastic material.

A further object of the invention is to provide new and improved extrusion screws for simul-' taneously forcing the plastic material through extrusion apparatus and plasticizing the material.

An apparatus illustrative of the invention includes an extrusion screw having a threaded 4 Claims. (CI. 18-13) portion for advancing plastic material along an extrusion cylinder, and also having a blade for kneading the plastic material to plasticize it.

A complete understanding of the invention may be obtained from the following detailed description of an apparatus forming a specific embodiment thereof, when read in conjunction with the appended drawings, in which:

Fig. 1 is a fragmentary, horizontal section of an apparatus forming one embodiment of the invention;

Fig. 2 is a reduced, fragmentary, vertical section of a portion of the apparatus;

Fig. 3 is a fragmentary section taken along line 3-3 of Fig. 2;

Fig. 4 is a fragmentary section taken along line 4-4 of Fig. 2, and

Fig. 5 is a fragmentary section taken along line 55 of Fig. 2.

Referring now in detail to the drawings, there is shown in Fig. 1 a continuous extrusion apparatus for forming a covering 8 from a nonmetallic plastic material, such as a vulcanizable compound including rubber or a synthetic rub- 2 around a filamentary conductor 9, which may be bare or may be covered with a textile or plastic covering. Theextrusion apparatus includes a heated extrusion cylinder Ill having a cylindrical bore II formed therein in which a stock screw I2 is rotatably mounted. The stock screw is rotated 'by a shaft "(Fig 2) to force the plastic material under high pressure through an extruding head l4 (Fig. 1). The extruding head l4 includes a body member l5 having a tapered opening I 6, which forms a continuation of the bore II and communicates with a bore 20 formed in theextruding head transversely of the tapered opening I. A strainer 18 is positioned between the bore I I and the tapered opening It for straining over-sized particles from the material. An annular die holder 2| positioned in the exit end of the bore 20 has a counterbore 22 formed therein in which is mounted a forming die 23;

The conductor 9 is advanced toward the right, as viewed .in Fig. 1, by suitable conductor:

advancing means, such as a capstan (not shown).

through a core tube holder 25 and a core tube 28 extending from the core tube holder 25. The core tube holder is provided with an inclined concave surface 21 for deflecting the material toward the die 23. An aligning plate 3| maintains the die holder 2| and the core tube holder 25, and thereby-the die 23 and the coretube 28, centered relative to each other in the bore 20, and a retaining nut 32 holds these elements in the extruding head l4.

The bore I I (Fig. 2) in the extrusion cylinder III has a uniform diameter throughout its length and a smooth surface except for a portion inter mediate of the ends thereof, which has a plurality of helical grooves 4I40 formed therein having helical ribs 4l'-4I therebetween. The cylinder is provided with an opening 43 into which the plastic material may be inserted into the bore II. The stock screw I2 is provided with threads 45 and 46 for forcing the plastic material from the entrance and of the extrusion cylinder. II toward the right, as viewed in Fig. 2. S-shaped blades 41 and 4| extend from the threads 4! and 46, respectively. The threads '45 and 48 have a relatively short pitch and gradually diminish in pitch -from left to right. as viewed in Fig. 2, to the blades 41 and 48, which have very long pitches. The blades 41 and 48 are provided with convex faces 49 and 50 (Fig.4), which are the leading faces of these blades as the stock screw is rotated in a clockwise direction, as viewed in Fig. 6, b the shaft l3. Wide ber-like materiaL- or a thermoplastic material; I! edges II and '52 of the blades 41 and 4!, respecenemas tively. are spaced slightly from the wall of the bore Ii so that the plastic material may slip between the wall of the bore II and the edges El and flasthestockscrew ilisrotated.

s-shaped blades s1 and I similar to the blades II and 48 are spaced 90' from the blades 41 and II, respectively, and are provided with convex faces 59 and t and wide edges BI and 82 spaced slightly from the wall of the bore H. The blades 41 and 4| parallel the blades 51 and 58 and are substantially coextensive therewith. As the stock screw 12 is rotated by the shaft ll, the plastic material is kneaded by the convex faces 49, 50, 89 and ill, and is rolled over these faces and over the wide, fiat edges SI, 82, Si and 62, which exert a milling or shearing action on the material, which thoroughly plasticizes the plastic material. Fillets 65, 66, 61 and 88 in the blades prevent the material from being wedged so tightly as to be stuck between the wall of the extrusion bore II and the convex faces of the blades. Due to their long pitch, the blades would not have much delivery capacity with a smooth surfaced bore. Hence, the helical grooves 40-40, which tend to advance the plastic material toward the right, as viewed in Fig. 2, are provided to give added delivery capacity. Also, the right ends of the blades have a relatively short pitch to force the material through the bore.

The depth of the blades 41, 48, 51 and 58 decreases from a substantial depth at the left end of the blades, as viewed in Fig. 2 and shown in Fig. 4, to substantially zero at the right ends of the blades, as shown in Fig. 5, so that the plastic material is compressed greatly as it is forced through the portion of the extrusion bore I I along which the blades extend, and all of the material is severely worked. Threads I and 16 extend from the blades 51 and 58 and decrease constantly in pitch from the left ends thereof to the right end of the screw II, as viewed in Fig. 2. The threads 15 and 16 are shallower than the threads 45 and 46, but are deeper near their juncture with the blades 51 and 5! than the blades ll, 48, 51 and 58, which are very shallow at this juncture. The material is squirted under a high pressure at the right ends of the blades 41, 48, 51 and 58 into the spaces between the relatively deep threads 15 and 16 where the material is under a relatively low pressure. This forcing of the material from a high pressure area to a low pressure area works the material.

The delivery actions of the threads 45 and 46 and the blades 41, 4t, 51 and 58 and the grooves 40-40 force the material through the portion of the bore I l coextensive with the blades. The root of the stock screw becomes larger in diameter from left to right, as viewed in Fig. 2, in the bladed portion of the screw so that the material is progressively compressed as it is forced through the portion of the bore ll coextensive therewith. The material empties from this portion into the much less restricted passages formed by the bore and the portion of the stock screw just beyond tively low pressure, unrestricted area, a relatively high pressure restricted area and a relatively low pressure, unrestricted area, which treatment works the material.

The constant decrease in pitch in the threads I5 and I6 toward the delivery ends thereof pro- 4 gresslveiy increases the pressure on the material asitisforcedalongthebore ii so thatthisportion of the stock screw tends to squirt the plastic material from the extrusion bore H as well as to advance it by the normal screw conveyor action and also works the material.

In the operation of the apparatus described hereinabove, the plastic material is fed into the left end of the extrusion bore II, as viewed in Fig. 2. The shaft l8 rotates the stock screw it in a clockwise direction, as viewed in Fig. 4, and the threads 45 and 46 advance the plastic material toward the right, as viewed in Fig. 2, to the blades 41, 48, t1 and 58 and progressively increase the pressure on the material. The material is rolled up on the convex faces 49, 50, I8 and 60 of the blades and is kneaded thereby against the wall of the bore II. The material slips between the flat edges of the blades and the wall of the bore H, and is milled therebetween.

The helical grooves 40-40 in the cylinder i I urge the material toward the right, as viewed in Fig. 2, when the material is revolved somewhat around the extrusion bore II with the blades 41, 48, 51 and it. This urging of the material by the grooves 40-40 and the pressure on the material being worked by the blades from the pressure of the plastic material being forced to the right by the threads 45 and 48 force the plastic material through the bladed portion of the stock screw it from the deep portion of the blades to the shallow portions thereof, and thence into relatively deep spaces between the threads 15 and It. The material then is advanced toward the right by the threads and I6, and is forced through the strainer it and the extruding head 14 inwhich it is formed into the covering 8 over the conductor 9 (Fig. 1).

The above-described stock screw l2 serves to advance the plastic material along the extrusion cylinder and, with the wall of the bore ll, severelykneads and mills the material as th material is forced therealong. The kneading and milling of the material together with the squirting of the material through restricted areas into much less restricted areas plasticizes the material thoroughly so that it may be formed into a high quality covering on the conductor 9. Furthermore, the working action of the stock screw greatly reduces, and may in some cases eliminate heating and working operations prior to the introduction of the material into the apparatus.

What is claimed is:

1. An apparatus for advancing and working plastic material, which comprises an extrusion cylinder having a bore therein, a portion of said bore being provided with a plurality of helical flutes in the periphery thereof and an extrusion screw mounted in the extrusion bore in the extrusion cylinder, said extrusion screw having a threaded portion with a short pitch for forcing plastic material through the extrusion here, said extrusion screw also being provided with a blade portion extending helically therealong substantially coextensive with the flutes in the periphery of the bore and having along pitch for kneading the material, said blade portion extending helically in one direction and said flutes extending helically in the direction opposite to that in which the blade portions extend.

2. An extrusion apparatus for advancing and working plastic material in a hollow cylinder, which comprises a stock screw having at least one helical thread extending along a predeteru mined portion of the length thereof for advancing plastic material along the hollow cylinder, said stock screw also being provided with at least one blade extending along a portion of the stock screw other than the portion thereof along which the helical thread extends, said blade being provided with a convex face on one side thereof and also being provided with a relatively flat tip, and means for rotating the stock screw in a direction in which the convex face of the blade is the leading face thereof, whereby the convex face on the blade kneads the plastic material against the wall of the cylinder and the flat tip of the blade mills the plastic material against the wall of the cylinder.

, 3. An apparatus for advancing and working plastic material, which comprises an extrusion cylinder having therein aibore of a predetermined diameter, a portion of the length of said cylinder having internal grooves therein, an

elongated member mounted rotatably in the bore and being provided with at least one thread for forcing plastic material along the bore, said thread extending along a predetermined portion of the member, said member also being provided with a kneading blade having a blunt tip and a sloping face, said blade being of a predetermined width such that there is clearance between the tip of the blade and the wall of the bore, and means for rotating the member in a direction in which the sloping face of the kneading blade is the leading face of the blade.

4. An apparatus for advancing and working plastic material, which comprises an extrusion cylinder having an elongated bore, and a stock 6 screw extending substantially coextensive with the bore in the cylinder, saidstock screw being provided with a threaded delivery portion, a bladed working portion and a threaded delivery portion extending therealong in the order stated, said threaded portions having threads having short pitches, said bladed working portion having a, blade extending therealcng substantially parallel to the longitudinal axis of the stock screw, said stock screw having a root portion, said root portion being relatively small along the delivery portions of the stock screw and tapering from a relatively small diameter to a relatively large diameter from one end of the blade to the other end thereof.

, GEORGE E. HIENNING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 591,575 Smith 1 Oct. 12, 1897 837,010 Vernstein Nov. 27, 1906 1,403,681 Gordon Jan. 17, 1922 1,762,368 Vandergrift June 10, 1930 1,935,050 Gordon Nov. 14, 1933 2,119,162 Hartner May 31, 1938 2,319,859 Hale May 25, 1943 2,367,394 Grimths Jan. 16, 1945 2,370,469 Johnston et a1 Feb. 27, 1945 2,370,952 Gordon Mar. 6, 1945 2,407,503 Magerkurth et al. Sept. 10, 1946 

